Effects: Expand Appearance and export give each Transform copy of a gradient path its own gradient (#2490)

A path with a Transform effect that makes copies and a gradient was still merged into one path by bake_leaf and expand_leaf, so the gradient spanned every copy. Route it through reshape / expand_outlined like the renderer does.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/effects/src/bake.rs

@@ -120,6 +120,13 @@ fn bake_node(d: &mut Document, n: &Node) -> Option<Node> {
         let m = reshape(n, symbol.as_deref())?;
         return Some(bake_node(d, &m).unwrap_or(m));
     }
+    // A path whose Transform effect copies it with a gradient: each copy an object of its own, so
+    // its gradient fits it rather than spanning every copy.
+    if crate::has_gradient_copies(n)
+        && let Some(m) = reshape(n, None)
+    {
+        return Some(bake_pieces(d, m));
+    }
     // Groups and layers: Pathfinder, geometry effects and their own fills and strokes (type that
     // Transform effects only move stays type). The new pieces (results, outlines, copies, the
     // fills' and strokes' art) get ids of their own.
@@ -968,4 +975,36 @@ mod tests {
         // An effect that also scales.
         assert!(transform_offsets(&[json!({"moveH": 10, "scaleH": 50})], &square).is_none());
     }
+    /// A 10 pt square painted with a red to blue gradient and a Transform effect with 2 copies.
+    fn gradient_copies(id: u64) -> Node {
+        use vectorcraft_color::{Gradient, GradientKind, GradientPaint, GradientStop};
+        let stops = vec![GradientStop::new(0.0, Color::rgb(1.0, 0.0, 0.0)), GradientStop::new(1.0, Color::rgb(0.0, 0.0, 1.0))];
+        let paint = Paint::Gradient(Box::new(GradientPaint::new(Gradient { kind: GradientKind::Linear, stops })));
+        let mut n = Node::path(NodeId(id), shapes::rectangle(Rect::new(0.0, 0.0, 10.0, 10.0)), Appearance::basic(paint, Paint::None, 0.0));
+        n.appearance.effects.push(fx("distort.transform", json!({"moveH": 30, "copies": 2})));
+        n
+    }
+
+    /// The paths under `n` that paint a gradient fitted to their own 10 pt box, left to right.
+    fn gradient_pieces(n: &Node) -> Vec<f64> {
+        let mut out = vec![];
+        let mut walk = vec![n];
+        while let Some(n) = walk.pop() {
+            match n.children() {
+                Some(ch) if !matches!(n.kind, NodeKind::Compound { .. }) => walk.extend(ch.iter().map(|c| &**c)),
+                _ => {
+                    assert!(matches!(n.appearance.fill_paint(), Paint::Gradient(_)), "{n:?}");
+                    out.extend(n.geometric_bounds().map(|b| b.width()));
+                }
+            }
+        }
+        out
+    }
+
+    #[test]
+    fn exporting_a_path_with_a_transform_gives_each_copy_its_own_gradient() {
+        let d = bake_document(&doc_with(gradient_copies(50))).unwrap();
+        // Three squares of their own, not one path spanning all three.
+        assert_eq!(gradient_pieces(d.node(NodeId(50)).unwrap()), vec![10.0; 3]);
+    }
 }

crates/effects/src/reshape.rs

@@ -198,10 +198,15 @@ pub fn reshape(n: &Node, symbol_art: Option<&Node>) -> Option<Node> {
     as_art(n, symbol_art)
 }
 
-/// `n` (see [`needs_outline`]) as plain art for Expand Appearance: [`reshape`]d when it has
+/// `n` (see [`needs_outline`], or a path with [`has_gradient_copies`]) as plain art for Expand
+/// Appearance: [`reshape`]d when it has
 /// geometry effects, else type with fills or strokes of its own outlined, in the same form. `None`
 /// when it has neither.
 pub fn expand_outlined(n: &Node, symbol_art: Option<&Node>) -> Option<Node> {
+    // A path whose Transform effect copies it with a gradient: each copy an object of its own.
+    if has_gradient_copies(n) {
+        return as_art(n, symbol_art);
+    }
     let own_paint = matches!(n.kind, NodeKind::Text(_)) && !n.appearance.items.is_empty();
     if !needs_outline(n) || (geometry_effects(n).is_empty() && !own_paint) {
         return None;

crates/engine/src/cmd/effectcmd.rs

@@ -504,10 +504,11 @@ pub(crate) fn expand_node(d: &mut Document, id: NodeId, brushes: &[vectorcraft_b
                     expand_pieces(d, &mut m, false, &mut stroke_art);
                     m
                 })
-            } else if matches!(n.kind, NodeKind::Path { .. } | NodeKind::Compound { .. }) {
+            } else if matches!(n.kind, NodeKind::Path { .. } | NodeKind::Compound { .. }) && !effects::has_gradient_copies(&v) {
                 effects::expand_leaf(d, &v, &mut stroke_art)
             } else {
-                // Type, images, symbol instances, live objects: through their outlines.
+                // Type, images, symbol instances, live objects (and paths whose Transform effect copies
+                // them with a gradient): through their outlines.
                 let symbol = match &n.kind {
                     NodeKind::SymbolInstance { symbol, .. } => d.symbols.iter().find(|s| s.name == *symbol).map(|s| s.art.clone()),
                     _ => None,
@@ -995,4 +996,27 @@ mod tests {
         assert_eq!(ch.len(), 1);
         assert!((ch[0].geometric_bounds().unwrap().width() - 50.0).abs() < 1e-6);
     }
+    #[test]
+    fn expand_appearance_gives_each_copy_of_a_transform_its_own_gradient() {
+        use vectorcraft_color::{Color, Gradient, GradientKind, GradientPaint, GradientStop, Paint};
+        let (mut s, id) = session_with_rect();
+        let stops = vec![GradientStop::new(0.0, Color::rgb(1.0, 0.0, 0.0)), GradientStop::new(1.0, Color::rgb(0.0, 0.0, 1.0))];
+        let ramp = Paint::Gradient(Box::new(GradientPaint::new(Gradient { kind: GradientKind::Linear, stops })));
+        s.edit("gradient", |d, _| {
+            let n = d.node_mut(id).unwrap();
+            n.appearance.set_fill(ramp);
+            Ok(())
+        })
+        .unwrap();
+        s.execute("effect.apply", &json!({"effect":"distort.transform","ids":[id.0],"item":null})).unwrap();
+        s.execute("effect.setParams", &json!({"index":0,"params":{"moveH":150,"copies":2},"ids":[id.0],"item":null})).unwrap();
+        s.execute("effect.expandAppearance", &json!({"ids":[id.0]})).unwrap();
+        let mut boxes = vec![];
+        node(&s, id).walk(&mut |n| {
+            if matches!(n.kind, NodeKind::Path { .. }) && matches!(n.appearance.fill_paint(), Paint::Gradient(_)) {
+                boxes.push(n.geometric_bounds().unwrap().width());
+            }
+        });
+        assert_eq!(boxes, vec![100.0; 3], "three squares, each with its own gradient");
+    }
 }